Theft of audio apparatuses mounted on automobiles (hereinafter a car audio apparatus) has become an increasingly serious problem. Therefore, there is a demand for effective antitheft means. Antitheft means presently adopted are classified into three major categories:
(1) A car audio apparatus has a handle and is detachably mounted on an automobile. When a driver (owner) does not use the car audio apparatus in the automobile and gets out of the automobile, he or she can take the audio apparatus out of the automobile by pulling the handle.
(2) A front panel having various operation keys and a display portion is designed to be capable of separating from a main body portion of a car audio apparatus. When the audio apparatus is not used, only the front panel is taken out of the automobile.
(3) A password, or a unique code, has been previously registered in a car audio apparatus. When a driver gets into the automobile and tries to use the car audio apparatus, he or she must enter a correct code, which is the same as the registered password or unique code, into the car audio apparatus. The use of the car audio apparatus is not allowed unless the entered code agrees with the previously registered code.
With the system (1) described above, the whole car audio apparatus must be taken out. Since the whole car audio apparatus is heavy and bulky, it is inconvenient to carry the car audio apparatus.
With the system (2), if a thief who stole the main body portion of the audio apparatus buys only a front panel of the same type later, then the main body portion of the audio apparatus will be usable with the front panel. Consequently, this system is not perfect as an antitheft means.
With the system (3), whenever the owner gets into the automobile, he or she must enter the unique code. Hence, this is troublesome.